Lead and cadmium at very low doses affect in vitro immune response of human lymphocytes

The effect of lead chloride and cadmium chloride on in vitro immunoglobulin (Ig) production by human lymphocytes was investigated. After 7 days in culture, lead added in the range of human exposure (207-1035 micrograms/liter) significantly enhanced Ig production either when cells were activated by pokeweed mitogen (PWM) or not. The effect was dose-dependent and was related to the Pb we measured in the extracellular medium and in the cells. Independently of the mitogen addition, about 2% of the Pb added was accumulated in the cells, most being associated with the nuclear fraction. Those findings suggest that the Pb effects could depend on its uptake and distribution in the cells. Cadmium added in the 50-500 nM range exhibited a dose-independent mitogenic activity in unstimulated cells, whereas the Ig secretion was not significantly affected by Cd when cells were PWM-activated. A considerable intraindividual variability, however, was observed when blood donors were separately examined, with both an increase, a decrease, or no variation on Ig production. Furthermore, higher percentages of Cd were accumulated in the nuclear fraction, and lower in the cytosol and precipitate, in PWM-activated compared to resting lymphocytes. Genetic factors could be of importance for the observed variability of the immune response to cadmium, and we support the hypothesis that differences in the metallothionein (MT) inducibility could play a role.